Stairs

ABSTRACT

A staircase and method of constructing it wherein steps of generally triangular cross section have angles formed by the three sides determined in accordance with a prescribed formula, the steps mounted to a stringer with one side of the step substantially horizontal and a selected one of the two other sides mounted to the top of the stringer. The step mountings are located in accordance with the prescribed formula. The stringer is mounted between two floors inclined within a range of angles.

United States Patent Guillermo Fuemw FOREIGN PATENTS 801,232 12/1950Germany Primary Examiner-Reinaldo P. Machado Attorney- Kingsland,Rogers, Ezell, Eilers & Robbins ABSTRACT: A staircase and method ofconstructing it wherein steps of generally triangular cross section haveangles formed by the three sides determined in accordance with aprescribed formula, the steps mounted to a stringer with one side of thestep substantially horizontal and a selected one of the two other sidesmounted to the top of the stringer. The step mountings are located inaccordance with the prescribed formula. The stringer is mounted betweentwo floors inclined within a range of angles.

PATENTED AUG24 I971 SHEET 1 [1F 2 STAIRS BACKGROUND or THE INVENTIONcarpenter must usually custom fit the stairs at the construction site.Also, the designs of staircases used prior to this invention oftenrequired custom fabrication of each staircase to insure proper fit anddesign. I

In this regard there is a formula well known in the art, which gives therelationship between the vertical distance between thefto ps of twosuccessive steps and the effective width of the steps. This formula is2R+T=25 inches, where R is the vertical distance in inches and T is thewidth in inches. Stairs designed in accordance with this formula givethe most natural stepping arrangement. It has, also been found that thevalue of R should be-within the range of approximately 7-8 inches.Values of R outside this approximate range render the stairsuncomfortable for use.

Thus designers try generally to design stairs in accordance with theabove formula and with values of R within this approximate range.

Therefore, it would be very desirable to design a staircase the. partsof which could be fabricated at the factory and which would fit anydesignrequirement within a specific range of values of R. For example,it would be desirable to design such a staircase which would fit anydesign requirement within R variations of from 7-8 inches and maintainthe relationship of R to T, as prescribed by the formula-for any ofthese variations; This invention is such a staircase.

BRIEF SUMMARY OF THE'INVENTION The staircase of this invention includesone or more stringers mounted between the floors to be connected by thestairs. Also included are a plurality of steps or treads which aremounted to rest on the top of the stringer. The steps are of generallytriangular cross section with one side of the step being substantiallyhorizontal for use as the stepping surface, and the other two sides eachbeing potential mounting surfaces. The angles formed by the sides of thesteps are determined in accordance with the formula 2R+T=25 inches, asarefthe locations of the means for mounting the steps to the stringers.The stairs and stringers can be prefabricated and the mounting locationspredetermined at the factory for a given range of values of R, so thatinstallation at the job site can be accomplished quickly and easily andwithout the need to customize to particular design requirement (so long,of

- course, as the design requirement is within the range of R for whichthe stairs were fabricated). Stairs designed for ranges of R from 7-8inches will nearly always fit the requirement since this isthe normalcomfort range. A single-step design of this invention will accommodatethis entire range and always maintain the formulated R-T relationship.

Because the stepping surface will vary approximately oneeighth' inchfrom horizontal over this range of R, adjustments may be provided tolevel the stepping surface. However, because the variation fromhorizontal is so slight, the adjustmentsmay be omitted if desired.

Various types of handrails may be mounted to the steps or stringers.Also, because the steps rest on the stringers, the stringers beingmerely for support, the stringers may be of any of several types andsizes. The steps themselves can be fabricated of any of severalmaterials conventionally used.

BRIEF DESCRIPTION OF THE DRAWING 1 FIGS. 1-6 are schematic illustrationsshowing the stair construction ofthis invention for various stringerangles;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Because the stairs ofthis invention are designed to fit within a range of designrequirements, it is first necessary to determine what the necessaryrange is. In this regard there is a for- I mula well known to the art,as follows: 2R+T=25 inches. This formula gives the relationship betweenR and T where R is the vertical distance between the tops of twoadjacent stair steps and T is the effective width of the steppingsurface of each of the steps. This formula is very old in theart, andformulates what has been found to be the most natural steppingarrangement, that is, where this relationship between R and T is notmaintained the stairs are uncomfortable for use. Therefore, it isdesirable in the design of any stairs to maintain this relationship.It'has also been found desirable to maintain R (the vertical distancebetween the tops of two adjacent steps) within a range of 7-8 inches,again it having been found that values of R less than 7 inches orgreater than 8 inches result in an uncomfortable stair design.Therefore, by far the most common stair designs are designed inaccordance with the above formula and with values of R ranging from 7-8inches. Obviously, as R increases, the value of T decreases, and theangle of inclination between the stairs and the floors which it connectsalso increases. Therefore, as an example, it will be shown how one stairdesign of this invention can be used to accommodate all stair slopes asR varies between 7 and 8 inches, and still maintain the relationshipbetween R and T set forth in the above formula.

Referring to F IG.. 1, there is shown schematically, two steps 10 and11, of generally triangular cross section mounted on a stringer 12. Aline 13 represents the floor. The angle f is the angle between thestringer 12 and the floor 13. The steps 10 and 11 have a substantiallyhorizontal stepping surface b and mounting surfaces c and d. Each stephas front and rear edges 14 and 15 respectively as shown in the drawing.The distance A is the distance between the tops of the steps 10 and 11,and the distance B is the width of the effective stepping surface ofeach of the steps. From the formula 2R+T=25 inches, where R is 7 inches,T is equal to 1 1 inches. With this information the value of the angle fcan easily be determined using trigonometric equations as follows:

tanj -7/ ll=0.636 f=3230' In like manner the angle f can be determinedfor any value of R. Where R equals 8 inches, T is equal to 9 inches andthe value of the angle f is given as follows: tan f=8/9=0.88, f= 4130.Hence it can be seen that as R varies from 7 to 8 inches, the angle fvaries from approximately 3230 to 4130 and that the value of T variesbetween 1 1 inches and 9 inches.

values of R. This is particularly important because of what happens tothe effective width of the steps as R, and, therefore, the angle ofinclination of the stringer, increases.

In FIG. 1, A is 7 inches so that the effective width B, of the steps 10and 11 is ll inches in accordance with the formula 2R+T==25 inches,therefore, the steps are mounted so that the front edge 14 of the step11 is vertically aligned with the back edge 15 of the step 10. Thisallows the entire width (l 1 inches) of the stepping surface to be used.FIG. 3 illustrates steps having the same dimensions and mounted the samedistance apart on the stringer 12 with the same faces d resting on thestringer 12. With R equal to 7% inches the angle f equals 36. As theangle f varies from 3230 to 36 the front edge 14 of the step 11 will becaused to overlap the back edge 15 of the step 10 approximatelythree-quarter inch. This in effect reduces the efi'ective steppingsurface B of the step 10 to 10% inches which is exactly in accordancewith the formula 2R+T=25 inches. Hence, it can be seen that as the anglef increases the effective stepping surface B decreases to values whichmaintain the relationship between R and T in accordance with theformula.

Also, as the angle f increases, the stepping surface b will deviate fromhorizontal. That is, if the stepping surface b is horizontal when theangle f equals 34 it will slope to the front as f increases and to therear as f decreases. Slight slopes to either the front or the rear areacceptable and even desirable in some cases, but excessive slopes suchas for example, onefourth inch or more are not desirable. In this regardit is found that by using either side or d of the step as mountingsurfaces, and by appropriately choosing the angles formed by the sidesof the steps, the deviation j from horizontal of the stepping surfacecan be kept to a maximum of approximately one-eighth inch. Hence, as Rvaries between 7 and 8 inches the maximum deviation j from horizontal ofthe stepping surface of each of the steps will be approximatelyone-eighth inch in either the forward or rearward direction. Such adeviation is practically unnoticeable to the user and in some casesdesirable for cleaning purposes.

This optimum condition can be obtained where the angle y between thestepping surface b and the surface d of each of the steps isapproximately 34 and the angle x between the stepping surface b and thesurface c is approximately 38. With a step so constructed the surface dis used for the mounting surface for angles of inclination between 3230and 37 and the surface c is used as the mounting surface for angles ofinclination between 37 and 4130. FIGS. 1-6 illustrate the deviationsfrom horizontal of the stepping surface b between angles of inclinationof 3230 and 4130. FIG. 1 shows a rearward deviation from horizontal ofapproximately oneeighth inch using mounting surface d and FIG. 6 shows aforward deviation from horizontal of approximately one-eighth inch usingmounting surface c.

Hence, FIGS. 1-6 illustrate how one step design can accommodate stringerangles of from approximately 3230 to 4130 corresponding to values of Rfrom 7-8 inches while maintaining the formulated relationship between Rand T and with maximum stepping surfaces deviation from horizontal ofapproximately one-eighth inch.

FIG. 7 illustrates a typical stair design of this invention. There isshown a lower floor 30 and an upper floor 31, a stringer 32 is mountedto the floors 30 and 31 by any suitable means such as angle brackets 33and 34. A tread or step 35 designed as described above, is mounted withits appropriate mounting surface 36 resting on the top of the stringer32. The step 35 is fastened to the stringer 32 by any suitable meanssuch as a bolt 37 and an inserted nut 38. A cover-board 40 may beinserted between the stringer 32 and the steps 35 if desired. Thecover-board 40 is simply used to cover the space between the steps 35. Abaluster 41 is mounted to the step 35 by various means as will behereinafter described.

FIGS. 8 and 9 are schematic illustrations showing how wedges 20 can beinserted under either the bottom or top edge of the mounting surface tolevel the stepping surface where deviations occur. The wedges may beomitted if desired, since the maximum deviation of approximatelyone-eighth inch is practically unnotieeable.

FIG. shows the versatility of the stairs design of this invention in thematerials from which the steps may be constructed. The step 43 isconstructed from solid wood, such as oak. The step 44 has a moldedplywood bottom 45 and a solid top 46. The step 47 has a molded plywoodbottom 45 and a vinyl asbestos surface 48. The step 49 is fabricated ofconcrete with an exposed aggregate top 50. A mounting insert 51 is usedfor mounting the step to the stringer. The step 52 is constructed ofconcrete with a smooth surface 53 and inserts 54 in the side of the stepfor supporting the baluster. The step 55 is still another type of stepfabricated from metal. This step is constructed of two angle brackets 56each constructed in accordance with the design described above which aremounted on a pair of stringers (not shown). The stepping surface 57 is ametal grating. Holes 58 are provided on each of the mounting surfacesfor mounting the brackets 56 to the stringers. In this embodiment,instead of wedges, leveling screws 59 are provided for leveling thestepping surface b of each of the steps. Holes (not shown) can beprovided in the grating 57 for receiving balusters, which can then bemounted to the sides of the brackets 56. The step 60 shows a similarstep construction only with the metal grating replaced by concrete slab61. The concrete slab 61 is reinforced with a plurality of steel bars62. A hole (not shown) may be provided in the concrete slab to receive abaluster for mounting to the angle brackets 56.

FIG. 11 shows a variety of stringers which may be used with thisinvention. The stringer 70 is composed of a 2X6 wooden support 71 withone-fourth inch plywood at the top 72 and bottom 73. The steps aremounted to the stringer with bolts 74 and angle brackets 75. A l 6 inchclosure board 76 may be provided to hide the bolts 74. Stringers 78 and79 are other types of wood stringers similar to the stringer 70. Thestringer 78 includes a maple core 80 between oak supports 81 and 82. Thestringer 79 is fabricated simply of 2X6inch oak. The stringers 90, 91,92, and 93 are various types of metal stringers. The stringer is a metalangle stringer. The stringer 91 is a metal angle stringer with a metalcover plate 94 to hide the mounting bolts. The stringer 92 is a metalI-beam stringer, and the stringer 93 is a metal stringer of open webconstruction.

FIG. 12 illustrates various types of baluster mounts that can be usedwith the steps of this invention. The mount illustrates a baluster 101mounted to the side of the step with lag bolts 102. The mount 103illustrates a baluster 104 with a threaded end 105. The end 105 isinserted through a hole in the stepping surface b, and is threaded intoan inserted nut 106. The mount 107 shows a baluster 108 inserted intoholes 10? and 110 that extend through the stepping surface b and theunused mounting surface 111 of the step with a stop plate 112 forlimiting the penetration of the baluster 108 into the step. Obviously,the balusters can be made of many different materials and can be used incombination with a great variety of hand rails.

Itshould now be evident that one of the features of this invention isthe great variety of materials and accessories that can be used. This isparticularly true of the stringers. Because the steps are not insertedinto the side of the stringer as is done in many of the conventionalstep designs, it is possible to use stringers of substantially smallercross section. In many of the old step designs the. stringers had to be10 inches wide to accommodate the necessary width of the steppingsurface. Notice in FIG. 11 that a stringer width of 6 inches issufficient to support the steps of this invention resulting insubstantial savings in, materials and expense.

Hence, this invention provides a stair construction that can beprefabricated with a great variety of materials and accessories to fit awide range of design requirements without changing the stair design, andstill maintain the formulated relationship between R and T.

Various changes and modifications may be made within the purview of thisinvention as will be readily apparent to those skilled in the art. Suchchanges and modifications are within the scope and teaching of thisinvention as defined by the claims appended hereto.

1. A stair construction for connecting adjacent floors comprising atleast one stringer mounted between the two floors, a plurality of stepsmounted on the stringer, each of the steps having a generally triangularcross section at least where the step is mounted on the stringer, oneside of the triangle defining a substantially horizontal steppingsurface and the other two sides defining potential mounting surfaces,the angles between each of the other sides and the stepping surfacebeing such that with the step mounted to the stringer on one mountingsurface the stepping surface is substantially horizontal through afirstprescribed range of stringer inclination angles, and with the stepmounted on the stringer on the other mounting surface the steppingsurface is substantially horizontal through a second prescribed range ofstringer inclination angles, means associated with each of the other twosides and the stringer for mounting the steps to the stringer, with theselect one of the other two sides resting on top of the stringer so thatthe stepping surface is nearest to horizontal, the stringer beingmounted at an angle of inclination of any angle of theranges of angles.

2. The stair construction of claim 1 wherein the angles between theother sides and the stepping surface and the location of the mountingmeans are determined in accordance with the formula 2R+T=25 inches,where R is the vertical distance in inches between the tops of twosuccessive stepping surfaces, and T is the width in inches of theeffective stepping surface.

3. The stair construction of claim 2 wherein the second range of anglesof inclination at which the stringer can be mounted is continuous withthe first to define a continuous total range of stringer inclinationangles.

4. The stair construction of claim 3 wherein the total range of stringerinclination angles is from approximately 32 to 42.

5. The stair construction of claim 2 wherein the angles formed by theother two sides and the stepping surface are approximately 34 and 38.

v 6. The stair construction of claim 2 including means for leveling thestepping surface.

7. The stair construction of claim 1 wherein the steps are of constantgenerally triangular cross section.

8. The stair construction of claim 1 wherein the mounting meansassociated with each of the other two sides and the sembly.

. variety of stringer inclinations comprising the steps of constructinga plurality of generally triangular cross section steps at least wherethe steps are mounted on a stringer, with one side of each of the stepsdefining a substantially horizontal stepping surface and the other twosides potential mounting surfaces, and with the angles formed by each ofthe mounting surfaces and the stepping surface determined in accordancewith the formula 2R+T=25 inches, where R is the vertical distance ininches between the tops of two successive stepping surfaces, and T isthe width in inches of the effective stepping surface, providing meansfor mounting the steps to a stringer with either of the mountingsurfaces resting on the topof the stringer in accordance with theformula 2 R+T=25 inches, mounting the stringer between the floors to beconnected by the stairs with an angle of inclination within a range ofangles resulting in a deviation from horizontal of the stepping surfaceof approximately one-half of an inch or less with the steps mounted onthe select one of the mounting surfaces which provides the most nearlyhorizontal orientation of the stepping surface, and mounting the stepswith the select one of the two mounting surfaces resting on the top ofthe stringer so that the stepping'surface is nearest to horizontal.

10. The method of claim 9 wherein R varies from approximately 7-8inches.

1 l. The method of claim 9 wherein the step of constructing a pluralityof steps is performed with the angles formed by the mounting surfacesand the stepping surface being approximately 34 and 38.

12. The method of claim 9 wherein the step of mounting the stepscomprises placing the steps in the mounting position on the stringerwith the select one of the two mounting surfaces resting on the top ofthe stringer so that the stepp ng surface 15 nearest to horizontal,leveling the stepping surface as necessary and securing the steps to thestringer.

13. The stair construction of claim 2 wherein the angles between theother sides and the stepping surface are selected such that the maximumdeviation of the stepping surface from horizontal through the ranges ofinclination angles is approximately one-half inch.

1. A stair construction for connecting adjacent floors comprising atleast one stringer mounted between the two floors, a plurality of stepsmounted on the stringer, each of the steps having a generally triangularcross section at least where the step is mounted on the stringer, oneside of the triangle defining a substantially horizontal steppingsurface and the other two sides defining potential mounting surfaces,the angles between each of the other sides and the stepping surfacebeing such that with the step mounted to the stringer on one mountingsurface the stepping surface is substantially horizontal through a firstprescribed range of stringer inclination angles, and with the stepmounted on the stringer on the other mounting surface the steppingsurface is substantially horizontal through a second prescribed range ofstringer inclination angles, means associated with each of the other twosides and the stringer for mounting the steps to the stringer, with theselect one of the other two sides resting on top of the stringer so thatthe stepping surface is nearest to horizontal, the stringer beingmounted at an angle of inclination of any angle of the ranges of angles.2. The stair construction of claim 1 wherein the angles between theother sides and the stepping surface and the location of the mountingmeans are determined in accordance with the formula 2R+T 25 inches,where R is the vertical distance in inches between the tops of twosuccessive stepping surfaces, and T is the width in inches of theeffective stepping surface.
 3. The stair construction of claim 2 whereinthe second range oF angles of inclination at which the stringer can bemounted is continuous with the first to define a continuous total rangeof stringer inclination angles.
 4. The stair construction of claim 3wherein the total range of stringer inclination angles is fromapproximately 32* to 42*.
 5. The stair construction of claim 2 whereinthe angles formed by the other two sides and the stepping surface areapproximately 34* and 38*.
 6. The stair construction of claim 2including means for leveling the stepping surface.
 7. The stairconstruction of claim 1 wherein the steps are of constant generallytriangular cross section.
 8. The stair construction of claim 1 whereinthe mounting means associated with each of the other two sides and thestringer are prelocated during the manufacture of the stair assembly. 9.The method of constructing a stair assembly to fit a wide variety ofstringer inclinations comprising the steps of constructing a pluralityof generally triangular cross section steps at least where the steps aremounted on a stringer, with one side of each of the steps defining asubstantially horizontal stepping surface and the other two sidespotential mounting surfaces, and with the angles formed by each of themounting surfaces and the stepping surface determined in accordance withthe formula 2R+T 25 inches, where R is the vertical distance in inchesbetween the tops of two successive stepping surfaces, and T is the widthin inches of the effective stepping surface, providing means formounting the steps to a stringer with either of the mounting surfacesresting on the top of the stringer in accordance with the formula 2 R+T25 inches, mounting the stringer between the floors to be connected bythe stairs with an angle of inclination within a range of anglesresulting in a deviation from horizontal of the stepping surface ofapproximately one-half of an inch or less with the steps mounted on theselect one of the mounting surfaces which provides the most nearlyhorizontal orientation of the stepping surface, and mounting the stepswith the select one of the two mounting surfaces resting on the top ofthe stringer so that the stepping surface is nearest to horizontal. 10.The method of claim 9 wherein R varies from approximately 7-8 inches.11. The method of claim 9 wherein the step of constructing a pluralityof steps is performed with the angles formed by the mounting surfacesand the stepping surface being approximately 34* and 38*.
 12. The methodof claim 9 wherein the step of mounting the steps comprises placing thesteps in the mounting position on the stringer with the select one ofthe two mounting surfaces resting on the top of the stringer so that thestepping surface is nearest to horizontal, leveling the stepping surfaceas necessary and securing the steps to the stringer.
 13. The stairconstruction of claim 2 wherein the angles between the other sides andthe stepping surface are selected such that the maximum deviation of thestepping surface from horizontal through the ranges of inclinationangles is approximately one-half inch.